This invention is generally concerned with data storage and access systems. More particularly, it relates to a portable data carrier for storing and paying for data and to computer systems for providing access to data to be stored. The invention also includes corresponding methods and computer programs. The invention is particularly useful for managing stored audio and video data, but may also be applied to storage and access of text and software, including games, as well as other types of data.
One problem associated with the increasingly wide use of the internet is the growing prevalence of so-called data pirates. Such pirates obtain data either by unauthorized or legitimate means and then make this data available essentially world-wide over the internet without authorization. Data can be a very valuable commodity, but once it has been published on the internet it is difficult to police access to and use of it by internet users who may not even realize that it is pirated. This is a particular problem with audio recordings, and, once the bandwidth becomes available, is also likely to be evident with video.
Over the past three or four years compressed audio sources have become increasingly widely available on web pages. One widely used audio data compression format is MP3 (MPEG-Audio Layer 3 of the MPEG1 compression algorithm), which is an internationally defined standard including a definition of compressed audio information such as speech or music. It relies on psycho-acoustic properties of human hearing to achieve very large data compression factors. It is thus feasible to download usefully long passages of music in a practically convenient short time. Pirate data suppliers have not been slow to realize the potential of this, and many unauthorized websites have sprung up offering popular industry considerable concern and there is an urgent need to find a way to address the problem of data piracy.